1. The tremendous advance accomplished in recent years on shore in the science of illumination has not been duplicated on board ship, and compared with that of a well designed office system, lighting in staterooms, crew's quarters and living spaces in general on naval vessels is well behind the latest practice on land. In this particular phase of increased efficiency the times have moved and we can hardly be said to have moved with them.
2. It is difficult to determine upon a definite lighting standard of so many foot-candles2 for each type of quarters on account of the large number of difficulties not encountered in shore installations, such as low deck height, deep beams, uniform cases, mess table stowage, ventilation, fire main and other large piping, causing the lights to be masked. The chief faults at present are (x) insufficient direct illumination; (2) insufficient general illumination;
(3) lamps presenting brilliant points in line of vision. As a result of this the efficiency of work of all kinds done below deck is considerably impaired and eye strain is greatly increased.
1 This paper is based entirely upon the belief that the tungsten filament will be so greatly improved as to overcome the defect of fragility; but even if this is not done, much could be accomplished in the interests of improved efficiency of lighting by a photometric study of the principal compartments of a ship, by the installation of metal or a metalized filament lamp, by the use of frosted bulbs, and by the introduction of prismatic glass reflectors.
2 A foot-candle is the unit for measuring the amount of light. The amount of light at a given point varies inversely as the square of the distance of the point from the source of light. Considering the source of light as emitting 16 candle-power, the amount of light one foot from the source will be 16 foot-candles; the amount of light two feet from the source will be 4 foot-candles; and the amount of light four feet from the source will be one foot-candle.
3. The lights now in use in the service are practically the original carbon filament lamps. Lately, however, there has been developed the " Gem " or "G. E." metalized filament, which is a greatly improved carbon filament type, giving a positive gain of 20 per cent in efficiency over the ordinary carbon lamp. This gain is due almost entirely to the higher temperature at which it is possible to burn the filament. The efficiency of a lamp is stated in watts per candle-power, and is obtained by dividing the total watts by the candle-power emitted. The ordinary carbon lamp burns about 3.1 watts per candle-power. The " Gem " lamp burns only 2.55 watts per candle-power. The life of this lamp is also considerably greater, and the light better, than that of the ordinary carbon filament.
4. But little attempt has been made to use this type of lamp in the service so far as the knowledge of the writer extends. The replacing of all lamps now in use throughout naval vessels after the life of the lamp has expired with even this G. E. metalized lamp would be a most welcome change to all concerned, and would add considerably to efficiency and comfort below deck.
5. If this can be said of the metalized filament, what can be said of the truly remarkable newly developed tungsten filament. It is this latest development of the latter filament that has made it at all possible to consider its use on shipboard. This tungsten is a strange metal, and an enumeration of a few of its characteristics may be of interest at this point.
6. It has a melting point of about 30000 C., which is higher than that of almost any other known metal, and thus is particularly well adapted for light producing. When at a high temperature it has in a remarkable degree the ability to remain stable, and at the same time possesses that very desirable attribute of any lighting filament known as "selective radiation," by which is meant that a very large proportion of its radiations are in the visible spectrum. These last two physical characteristics account in a large measure for the increased efficiency it is possible to obtain by means of this element.
7. Although the queen of metals in the question of melting points, strangely enough it oxidizes at a comparatively low temperature, and a filament becomes plastic and can be worked with more or less ease at a temperature as low as 275° C. When cold, however, the filament as formerly manufactured was exceedingly brittle and this until very recently has been the prime drawback to the development of the lamp, of which there will be more to be said later.
8. The original manufacture of the tungsten filament consisted of a process called " sintering, " which was nothing more nor less than a welding of a large number of small pieces of the metal at a very high temperature. While this general process was being experimented upon to obtain a stronger filament by some of the most expert engineers and chemists, the work of improving the mechanical connections of the filaments in the lamps themselves was making good headway. In the place of the first lamps, in which each separate thread of the metal was soldered in place separately and fused to a rigid support, a continuous thread was wound throughout and was not rigidly fastened at any point except at the leading-in wires. It is to be noted, however, that such a practice was not of course possible until the above " sintering" process had been so much improved as to admit of the manufacture of the filament in longer lengths, and even with this improvement, the greatest care is required at the point where the filament joins the leading-in wire. This type of lamp , presented a marked improvement, but for many practical purposes the lamp was still entirely too fragile, and, for use on shipboard, impossible. One discharge from a 12-inch gun would have put most of the lamps in the ship out of commission. This filament has been very aptly compared to glass, in that it has considerable tensile strength and can be bent; the smaller the diameter the more bending it will stand. When warm it becomes quite soft, but when cold is fragile and heavy, vibrations such as those due to gun-fire shattering it. This is rendered all the more difficult on account of the extremely small cross section of the tungsten filament (many times smaller than that of carbon, and too infinitesimally small and irregular at the same time to be accurately measured by any known means except electrically, the filament of a 25 watt lamp being only i/woo of an inch in diameter).
9. These improvements, first in the filament, then in the method of internally supporting it, and, finally, in supporting the entire fixture, have recently been more or less overshadowed by the discovery, after years of patient effort at the research laboratory of the General Electric Company, of a method of producing pure tungsten in the form of a continuous filament, so ductile as to be drawn into the finest wire, and possessing a truly extraordinary tensile strength. There can be no doubt that this discovery, coupled with the improvements above mentioned, will be the means of overcoming the defect of fragility, thus rendering the use of the tungsten light possible in all those places where this defect had precluded its adoption, one of the most important of which is on shipboard.3
ADVANTAGES OF INTRODUCING TUNGSTEN.
I. More Light.
10. The primary advantage to be obtained is more light. Any gain in this connection presupposes an actual need of additional light. That there is such a need will not be disputed for an instant by seagoing officers.
This is not the time nor the place to make any extensive criticism of the present system employed in lighting ships, but the efficiency of such a system can well be questioned from a scientific and practical standpoint when it is considered that the amount of light in the various spaces of a ship is calculated approximately as follows:3
11. The actual determination of the amount of light to be supplied in certain places seems to have received but scant attention.
3 A few tantalum lamps were tried some time ago on different vessels and were unfavorably reported on by the commanding officers on account of their fragile nature. The Bureau of Equipment is about to make a trial installation of tungsten lamps embodying many of the latest improvements. It is hoped that a more favorable report will be received on these later lamps and that the defects as they develop may be entirely overcome by the expert representatives of the leading companies. Surely the probability of receiving a contract to " tungsten " the navy should present to these companies a goal worthy of the efforts of their ablest engineers.
4 NOTE.—Taken from "Electrical Installations of the U. S. Navy" by Commander B. T. Walling, U. S. N., and Julius Martin, E. C., Master Electrician, Equipment Department, Navy Yard, New York.
“Room, Handling, Turret.—The lighting to be based on 500 cubic feet of space to each 16 candle-power fixed lamp…”
“Shop, General Work.—The lighting to be on a liberal basis approaching 500 cubic feet of space to each 16 candle-power fixed lamp…”
"Admiral's and Captain's Dining-room, Wardroom, Messroom.— Ceiling fixtures No. 1 for overhead lighting on the basis of 400 cubic feet to each 16 candle-power fixed light…”
To do this would require a little time and a few photometric tests in staterooms, wardrooms, firerooms, living quarters, etc., on ships actually in commission, but it could be done and, in the opinion of the writer, should be done, and a standard of lighting in certain locations accurately obtained as so many foot-candles, and the lights distributed on this more rational basis. To try to do this in an exact way in an engine-room would be impossible on account of the numerous obstructions, shadows, etc., and also on account of the large number of special lights for illuminating such special features as gage glasses, annunciators, manifolds, indicators, etc., but it is believed to be entirely practicable in many other places, and at least it would be possible to determine definitely just what is required, and thus make it easier to meet the requirements than at present.
12. This element of the problem solved, the actual distribution of the lamps to accomplish the above result, namely, the providing of a given number of foot-candles, say over a stateroom desk, would be fraught with many difficulties, and in many instances would have to be solved differently on each ship; but if the problem were attacked in this way, it is believed that a more efficient lighting system would be evolved, at the expense of less lights, wiring, conduit and fixtures.
13. Assuming an old installation on a ship, say of the California class, the installation of tungsten lamps in the place of the present carbon lamps, provided the former were fitted with suitable globes, etc., would easily effect an increased lighting efficiency of 40 per cent at an equal dynamo output, or, to put it another way, the same amount of light could be obtained as at present with a much less dynamo output, and hence saving of coal and water, and with a reduction in the number of lights and fixtures of at least 20 per cent. In a new installation, say of the 28,000-ton Oklahoma, it is believed, if the tungsten filament is sufficiently well developed by the time the lighting of that vessel is to be installed, that a lighting system can be installed that will give at least 30 per cent more light than that now on large battleships, that will weigh less in proportion by from 2 to 3 tons of dynamos, wiring, fixtures, conduit, hangers, spares, etc., and that will cost actually less in proportion.
14. It must be understood that the remodeling of an old system to burn tungsten lamps in sockets now provided for carbon, will necessitate the renewal of many fixtures, though not all, for the reason that we are dealing with a light of much more intrinsic brilliancy, a higher powered explosive, so to speak, requiring more care in its use. To replace all carbon lamps now in use with clear tungstens would actually give us a much poorer scheme than that now installed. A bare electric lamp has but little place in the illumination of any occupied space, such as crew's quarters, staterooms, etc., and the new lamps would require to be bowl frosted, and in many places, particularly staterooms, fitted with prismatic reflectors. The actual gain due to more light is impossible to measure, but in such a matter definite figures are perhaps not as potent as a consideration of such facts as the following: More light means better vision, less fatigue and more cheerful environment. Light stimulates; darkness depresses. Men work more rapidly and accurately in a bright light and away from depressing surroundings. Light reduces liability of errors and saves time.
2. Better Light.
15. Besides this increased light and the saving that can be effected in weight, we get a light of better quality; that is, one more nearly like sunlight and free from the yellow light pf the carbon filament.
3. Efficiency Retained Until Lamp Burns Out.
16. Tungsten lamps retain their efficiency much longer than carbon lamps, and while the average carbon lamp will burn down to as low as 50 per cent of its rated candle-power before its life is gone, tungsten, though having a longer life, burns out before it has fallen more than 10 per cent in candle-power. The enormous gain due to this property of the tungsten will not be appreciated until it is stated that a test of all carbon lamps in a large cruiser showed that over 6o per cent of the lamps were burning with less than 80 per cent of their rated power, due to the vaporizing of the filament causing a deposit of carbon to be formed upon the walls of the lamp, blackening them and reducing the luminous efficiency.
4. Renders Possible the Use of Frosted Globes.
17. Since tungsten leaves no deposit on the globe we can employ frosted globes throughout, thus very greatly overcoming that defect so frequent in lighting systems due to the brilliant incandescent filament directly in the line of vision. This defect is particularly prominent on shipboard (I) because of the low deck height and the necessity for the large number of bulkhead lights and (2) because carbon lamps with frosted globes fall 20 per cent in candle-power in one-half of the time required for the plain bulb (the total life, however, remaining the same), for which reason their use is now limited to absolute necessities.
5. Less Attention.
18. This feature of the tungsten also brings up another advantage which, though not as marked on board ship as on shore, is nevertheless appreciable, and this is that with a lamp that retains its full efficiency until burnt out, there is much less need of renewals and less attendance is required.
6. Wider Range of Voltage Regulation. Possible.
19. The tungsten lights admit of greater errors in voltage regulation without materially affecting the life of the lamps. For example, an increased voltage of 4.5 volts on a 125-volt circuit will halve the life of a carbon lamp, while to halve the life of a tungsten on a similar circuit would take an increase of about 6.25 volts.
7. Saving of Power.
20. The efficiency of the tungsten is so high, about 1.25 watts per candle-power as against 3.5 for the carbon, that a considerable saving in power can be effected and still produce a great deal more light.
DISADVANTAGES.
21. (I) The prime disadvantage will be the increased first cost. Not only will the lights themselves cost more, but it will be necessary to change the type of fixtures and globes now in use to accommodate the added brilliancy of the new light. In a new installation this can be entirely offset by the smaller first cost of a dynamo of less power than would be required with carbon, less conduit and hangers, fewer lights and fixtures, although providing much more light. But in thus increasing the efficiency of an existing system of carbon lights, there is no doubt but that the cost would be considerable. Much of this will undoubtedly be overcome by a reduction in the cost of the lamp as progress is made in improving the filament and the entire lamp.
22. (2) It will probably be necessary to carry the two types of lamps on all ships for some time to come, as it is doubtful if the tungsten filament will be developed to such a point as to admit of its use in a horizontal position for some years yet.
PRISMATIC REFLECTORS.
23. The adoption of tungsten and bowl frosted globes should be accomplished by the introduction of suitable reflectors. The increased efficiency that can be effected by proper use of this very valuable accessory is not thoroughly appreciated even by many who ought to be entirely familiar with the subject. The primary purpose of reflectors is to change the distribution of light by means of reflection in order to ( 1) increase the amount of illumination; (2) afford a protection to the eyes, and (3) improve the
appearance of the installation.
EFFICIENCY.
24. The bare carbon lamp, when used in connection with low deck height and white painted ceiling and bulkheads, provides a very considerable volume of light. The difficulty is that it is not controlled, the lamp throwing light in all directions, and no means is provided for concentrating it upon the plane it is desired to illuminate. The use of reflectors is not so simple as it appears and, like nearly all apparently easy everyday problems, should be approached in the light of a little applied science and engineering experience. The more or less recently devloped Holoplane ,reflectors or prismatic glass seem to furnish the most satisfactory candle-power distributions. As now manufactured, they consist of three general types; the extensive, intensive, and focusing, variations from these being made to suit almost every conceivable local arrangement. As yet it is not believed that any suitable type of Holoplane reflector has been developed for a bulkhead light, but it is believed that this, together with the much larger and more general problem involved in the extensive use of reflectors would be cheerfully solved, free of all charge to the government, by the illuminating engineers of the companies who would be only too glad to explore a field that offers such a large possibility for increased business and added efficiency for the naval service.
EYE PROTECTION.
25. The shade reflectors used to accomplish this end are usually opaque themselves, and while directing the light upon a given plane, they leave the bare lamp exposed, and a zone of darkness in the immediate vicinity of the lamp. The eye, looking from the light into the comparative darkness around it and back again to the light, suffers repeated shocks and the result is eye-strain and a probable permanent impairment of vision. A certain amount of general lighting should always accompany direct illumination, and the use of prismatic glass reflectors affords this general illumination.
APPEARANCE.
26. But little will be said under this heading, as the subject is one which must be considered almost entirely from a utilitarian point of view. It is believed, however, that even this sentimental phase of the matter may appeal to those who like to believe that our battleships are up-to-date in every particular, and who will enjoy the added cleanness and smartness presented by an installation of bowl frosted tungsten lamps fitted with suitable prismatic glass reflectors.